The use of classic laryngeal mask airway (cLMA) as a conduit for intubation is a known technique in pediatric difficult airway. We faced a unique problem during the management of an unanticipated difficult airway in a neonate while negotiating the endotracheal tube (ETT) through cLMA.

A 1-month-old infant, weighing 3.8 kg, had an unanticipated difficult airway with failure to intubate the trachea despite repeated direct laryngoscopic attempts. Adequate ventilation was achieved with cLMA size 1.0. A flexible fiberoptic bronchoscope (FOB; size 2.8) through cLMA showed grade 4 glottic view. [1] It was decided that a size 3.5 uncuffed ETT to be passed over the FOB and tracheal intubation attempted using cLMA as a conduit. Despite successfully negotiating the FOB into the trachea, we were unable to pass the 3.5- mm ETT through the cLMA 1.0. Subsequently, tracheal intubation was achieved with a size 3.0-mm ID uncuffed ETT through the same cLMA 1.0 by using the blind technique.

After removal of cLMA, we failed to pass the 3.5-mm ETT through the cLMA even with force. Later, while trying to negotiate 3.5-mm ETT through all (four in daily use) available cLMAs of size 1.0, we were able to pass the 3.5-mm ETT through only one cLMA. In other cLMAs, the ETT stuck in the shaft of the LMA after crossing the connector. The 3.5-mm ETT also passed through a freshly opened size 1.0 cLMA.

The size 3.5-mm ID uncuffed ETT should pass through size 1.0 cLMA, according to manufacturer's recommendation. There is no mention of the standard internal diameter of the shaft of LMAs in the available literature. Although manufacturers recommend that LMA be used up to 40 times after autoclaving, there have been reports of successful use of LMA up to 100 times. [2] In our institute, we use cLMA more than the recommended 40 times after testing. In the case reported, three of four LMAs, including the one that allowed passage of the ETT, had been used more than 40 times. The 3.5 mm ETT could not be passed through a cLMA, which had been used less than 40 times. It is not known whether autoclaving produces changes in the outer and inner diameter of shaft of LMA.

We recommend that before using cLMA as a conduit for intubation, the maximum size of tracheal tube that can be passed through a particular LMA should be checked before, to avoid unanticipated difficulties. Manufacturer's details about the internal diameter may be helpful for further evaluation of change in the diameter of shaft after autoclaving.